Effects of milk basic protein supplementation on bone density and bone metabolism markers in female college long-distance runners: A double-blind randomized controlled trial

Objective: It has been reported that long-distance runners have a high incidence of stress fractures. Milk basic protein has been shown to help build healthy bones in people of all ages. However, little is known about how milk basic protein function in athletes. Therefore, we clarified the effect of milk basic protein ingestion on bone mineral density and bone metabolism markers and decided to use it to reduce the incidence of stress fractures in athletes and improve bone strength. Methods: This was a double-blind, randomized controlled trial. The ingestion group was instructed to consume a soft drink containing 40 mg of milk basic protein, and the non-ingestion group was instructed to consume a 50-mL bottle of placebo soft drink daily for 6 months. Thirteen of the 14 participants, excluding one who declined to participate in the study, were stratified and randomized based on their baseline height, weight, and lumbar bone mineral density measurements; the ingestion group included six women, and the non-ingestion group included seven women. The survey included physical measurements, bone mass/density measurements, blood/urine biochemical tests, food ingestion frequency surveys, and menstrual and mileage surveys. The survey period was from May to December 2019. Results: There were no significant differences in the changes in bone formation, bone resorption, or bone quality markers between the two groups. However, when the bone formation rate (= bone formation marker/bone resorption marker) was calculated, a higher bone formation rate was observed in the ingestion group, although the difference was not significant. Regarding changes in bone mineral density, the radial cancellous bone mineral density tended to be higher in the ingestion group than in the non-ingestion group, and the lumbar spine bone mineral density was higher in the ingestion group. Conclusion: An increase in radial cancellous bone mineral density and lumbar spine bone mineral density were observed after ingestion of milk basic protein for 6 months. This indicates that the bone mineral density of athletes may increase.